I have had that same problem several times before.
Turns out to be a bad battery cable or where the ground cable is bolted to the engine.
You can't see it or any signs of it being bad.
Clean both ends of both cables, and if that don't work,take a set of jumper cables and bypass your battery cables.

I have seen battery cables that look good and still be disconnected inside the insulation.

Let us know how it turns out.

2-Ton

1967 GMC 9500 Fire Ladder Truck
"The Flag Pole"
In the Stovebolt Gallery
1946 2-Ton grain truck
1946 3/4-ton pickup,
1953 1-ton pickup
1957 1-ton flatbed dually,
1954 Pontiac Straight Eight
Of all the things I've lost in my life, I miss my mind the most!